text: There is an analogous form of the Grashof number used in cases of natural convection mass transfer problems. In the case of mass transfer, natural convection is caused by concentration gradients rather than temperature gradients.
  where
  and:
  *   is gravitational acceleration due to Earth
  *  is the concentration of species  at surface
  *  is the concentration of species  in ambient medium
  *  is the characteristic length
  *  is the kinematic viscosity
  *  is the fluid density
  *  is the concentration of species 
  *  is the temperature (constant)
  *  is the pressure (constant).